Federal Income Taxes - Schedule of Components of Future Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 56,781	$ 85,995
Mineral properties	7,237	10,152
Accrued vacation	17	29
Reclamation provision	224	41
Capital loss carryforwards	1,013	618
Restoration reserves	980	1,623
Capitalized transaction costs	912	1,140
Other	4,123	4,072
Deferred tax assets	71,287	103,670
Valuation allowance	(68,121)	(99,548)
Net deferred tax assets	3,166	4,122
Derivatives	(590)	(956)
Mineral properties, Turkey	(1,437)	(1,489)
Securities	(106)
Property, plant and equipment	(1,033)	(1,677)
Deferred tax liabilities	(3,166)	(4,122)
Net deferred tax asset (liability)